Penetration Grouting Research Articles

Penetration grouting diffusion and strengthening mechanism of sand layer with crucial grout

Ordinary Portland Cement (OPC), micro-fine Portland cement (MPC), micro-fine sulfur-alumina cement (MSAC) and effective micro-fine cementitious grout (EMCG) were adopted. A visual simulation test device for fixed pressure permeation grouting for sandy soil was designed, and osmotic spreading and strengthening tests were conducted. The time-dependent variation rules of spreading distance and slurry amount were analyzed, and the influence of grout type, sand gradation, and grouting pressure on the reinforcement result were studied. The strengthening mechanism of EMCG at different spreading distances was analyzed emphatically, the microscopic strengthening modes of grout-rock interface with different grouts were obtained, and the essential reinforcement differences of various grouts were revealed. Based on the Kozeny-Carman model, the generalized percolation coefficient was deduced. The results showed that grout types and particle mass fraction were key factors to determine injectability of fine sand, the effect of grouting pressure was not significant, and the injectability of EMCG was the most satisfied. At the water-binder ratio (W/B) of 1.0, the 3 d strength of EMCG reached 13.3 MPa, and it was 1.25, 1.37 and 2.46 times as those of OPC, MPC and MSAC, respectively. The 7 d strength of EMCG exceeded 70 % of its 28 d strength, the diffusion distance of EMCG exceeded 2 m for S2 sand (0.3–0.6 mm), and its 28 d strength of reinforced sand reached 2.18 MPa as the W/B of EMCG was 2.5. The dense C–S–H gels generated at the EMCG slurry-rock interface can effectively improve cementation strength of sand and grout.

Column-Hemispherical Penetration Grouting Mechanism for Newtonian Fluid Considering the Tortuosity of Porous Media

The intricate morphology of porous media can considerably affect the progression of penetration and the diffusion of grouting slurry. In this study, a Newtonian fluid’s refined seepage motion equation was proposed to incorporate the impact of tortuosity on the grouting process into gravel soil, and the column-hemispherical penetration grouting mechanism was analyzed using the method of theoretical analysis. Utilizing secondary-development programming techniques, a numerical simulation program was developed with COMSOL Multiphysics to model the penetration grouting mechanism of a Newtonian fluid in a column-hemispherical pattern, considering a medium’s tortuosity. The penetration grouting process of Newtonian cement into gravel soils was then simulated. Finally, the theoretical analysis, experimental values, and numerically simulated values were compared.The findings suggested that incorporating the tortuosity of porous media is more efficacious in depicting the penetration and diffusion behavior for Newtonian fluid grouting in porous media, as compared to omitting the tortuosity. The findings of this study contribute to a better understanding of grouting engineering in porous media strata, guiding practical design and construction.

Study on Mechanism and Verification of Columnar Penetration Grouting of Time-Varying Newtonian Fluids

Penetration grouting technology is an important technical means to improve the mechanical properties of gravel soil layers, and the time-varying characteristics of Newtonian fluid viscosity have an important influence on the morphology and effect of penetration grouting. However, these time-varying properties are not considered in the current research on the mechanism of Newtonian fluid penetration grouting. In this paper, by studying the basic rheological equation of Newtonian fluids and its dynamic viscosity time-varying law, the penetration motion equation of viscosity time-varying Newtonian fluids is discussed, by means of theoretical analysis and experimental research. Based on this, the time-varying viscosity Newtonian fluid columnar penetration grouting diffusion mechanism (TVNCPGDM) equation is derived, the application scope of the equation is analyzed and a grouting experiment is designed to verify it. The results show that the theoretical value of the grouting diffusion radius calculated by the TVNCPGDM equation, is closer to the experimental value than that obtained by the equation of columnar penetration grouting without considering the viscosity time-varying Newtonian fluid, with a 12.9% improvement in accuracy. This shows that the TVNCPGDM equation derived in this paper, can better reflect the diffusion law and diffusion morphology of column penetration grouting of Newtonian fluid, which changes with time in the injected medium; and the diffusion radius obtained for penetration grouting is more in line with the actual grouting engineering demands. The research results can provide some theoretical guidance for the actual grouting of loose gravel soil layers.

Experimental Study on the Shear Properties of Soil around Piles with Permeation Grouting

While post-grouting is frequently reported to improve the engineering performance of piles, the shear strength of the soil around piles is not well understood. To investigate the strengthening mechanism of soil around piles with permeation grouting, laboratory tests were carried out on homemade cement soil from the aspects of shear strength and microstructure characteristics. The evolution rule of the shear stress–shear displacement curve of grouting soil with different cement contents was analyzed, and the influence of grouting parameters on shear strength was explained. A composite exponential model describing the shear stress and shear displacement of permeation grouting silty clay was established. Furthermore, the influence of different cement content on changes in the microstructural characteristic parameters of the soil around piles was studied. The results show that penetration grouting has a positive effect on improving the shear strength of the soil around piles, and the failure mode of silty clay changed from elastic–plastic failure to brittle failure after grouting. Permeation grouting makes the particle structure denser, which limits the changes in pore arrangement and distribution. The shear failure of the soil around piles under permeation grouting obeys the Mohr–Coulomb criterion of failure. It is recommended to increase the grout diffusion radius during construction, considering the reinforcement effect of permeation grouting on the soil around piles.

Theoretical Research on Diffusion Radius of Cement-Based Materials Considering the Pore Characteristics of Porous Media.

In engineering, loose sandy (gravelly) strata are often filled with cement-based grout to form a mixed material with a certain strength and impermeability, so as to improve the mechanical properties of sandy (gravelly) strata. The tortuosity effect of sandy (gravelly) strata and the time-varying viscosity of slurry play a key role in penetration grouting projects. In order to better understand the influence of the above factors on the penetration and diffusion mechanism of power-law slurry, based on the capillary laminar flow model, this research obtained the seepage motion equation of power-law slurry, the time-varying constitutive equations of tortuosity and power-law fluid viscosity were introduced, and the spherical diffusion equation of penetration grouting considering both the tortuosity of porous media and time-varying slurry viscosity was established, which had already been verified by existing experiments. In addition, the time-varying factors of grouting pressure, the physical parameters of the injected soil layer, and slurry viscosity on penetration grouting diffusion law and the influencing factors were analyzed. The results show that considering the tortuosity of sandy (gravelly) strata and the time-varying of slurry viscosity at the same time, the error is smaller than the existing theoretical error, only 13~19%. The diffusion range of penetration grouting in the sandy (gravelly) strata is controlled by the tortuosity of sandy (gravelly) strata, the water-cement ratio of slurry, and grouting pressure. The tortuosity of sandy (gravelly) strata is inversely proportional to the diffusion radius of the slurry, and the water-cement ratio of slurry and grouting pressure are positively correlated with the diffusion radius. In sandy (gravelly) strata with a smaller particle size, the tortuosity effect of porous media dominates the slurry pressure attenuation. When the particle size is larger, the primary controlling factor of slurry pressure attenuation is the tortuosity effect of porous media in the initial stage and the time-varying viscosity of slurry in the later stage. The research results are of great significance to guide the penetration grouting of sandy (gravelly) strata.

Influence of Coupling Effects between Gravel Soil Porosity and Cement Grout Weight on Diffusion Laws and Morphologies of Penetration Grouting

The practice and theory of grouting engineering show that both injected medium porosity and grouting fluid weight play an important influence on the diffusion law and morphology of penetration grouting. However, the effects have not been well studied in the context of existing penetration grouting mechanisms. In this paper, the actual diffusion law and morphology of cement grout into the gravel soil are studied on the basis of indoor experiments, mathematical statistics, and theoretical analyses. Then, the three-dimensional space diffusion trajectory equation was quantitatively characterized. The influence of the coupling effect between gravel soil porosity and cement grout weight on diffusion morphologies of penetration grouting was discussed by the definition of the morphological deviation rate. Results show that actual penetration diffusion dimensions of cement grout into the gravel soil differ from that of theoretical values calculated by the penetration grouting mechanism, and its spatial diffusion morphology is approximated as ellipsoid. The coupling effect between gravel soil porosity and cement grout weight have a relatively significant effect on the diffusion morphologies of penetration grouting except for gravel soil with porosity <0.5 infiltrated by Newton-type and <0.4 by power-law-type cement grout, respectively. This influence is particularly significant when Bingham-type cement grout was penetrated into gravel soil with a porosity of >0.5. The research results can provide theoretical support and technical references for the practical grouting engineering of gravel soil.

Backfill grouting diffusion law of shield tunnel considering porous media with nonuniform porosity

Current studies usually do not consider the effect of spatially inhomogeneous distribution of formation parameters on grout diffusion caused by shield tail voids. To solve the above problem, this study proposes a nonuniform pore model for porous media formation and establishes a one-dimensional penetration grouting diffusion model considering the spatial nonuniformity of formation pores under the condition of constant grouting pressure. This model was used to analyze the penetration diffusion behavior of grout in the strata and the influence of parameters such as grouting pressure, water-cement ratio, and formation displacement. The numerical solution was provided by the finite element software COMSOL. According to the degree of cement particle blockage, it is pointed out that there is an injectability control zone in the grouting process. A one-dimensional visualized penetration grouting diffusion simulation system considering the shield tail gap was designed, and a grouting diffusion test was carried out with cement slurry. The results show that grouting pressure, water-cement ratio, and soil displacement have a significant influence on the grout deposition process. The higher the grouting pressure, the lower the water-cement ratio, the faster the formation turns into the non-injectable state. The grouting pressure has little influence on the injectable control zone, while the larger the water-cement ratio, the greater the displacement of the formation, and the farther the injectability control zone is from the grouting hole. By comparing the nonuniform pore model with grouting test, the rationality of the nonuniform pore model is verified, which provides guidance and a basis for backfill grouting.

Column Penetration and Diffusion Mechanism of Bingham Fluid Considering Displacement Effect

The diffusion progress of grout is hindered by groundwater, which means the diffusion distance cannot reach the designed values required in engineering for water plugging or reinforcement. In this study, based on the generalized Darcy’s law and the continuity equation of steady column penetration, a column diffusion mechanism for Bingham fluid, considering the displacement effect of grout on groundwater, is proposed. This diffusion mechanism is then validated by the penetration grouting experiments that have been previously performed. The influences of the grouting pressure, groundwater pressure, water–cement ratio and penetration coefficient of porous media on the diffusion radius are analyzed. Based on the Comsol Multiphysics platform, a three-dimensional numerical simulation program for this mechanism is developed using computer programming technology. Numerical simulations of the penetration and diffusion morphology of Bingham cement grout in porous media are then carried out. The results show that the theoretical calculation values of diffusion radius obtained from this mechanism are closer to the experimental values than those obtained from the column penetration grouting theory of Bingham fluid, without considering the displacement effect. The results of this study can provide theoretical support for practical grouting engineering.

Theoretical Research on Sand Penetration Grouting Based on Cylindrical Diffusion Model of Tortuous Tubes

The penetration paths of grouts in sand layers are tortuous, and there is no reasonable penetration grouting theory at present. By employing tortuous circular tubes as the internal penetration pore channels of the sand layer, the cylindrical diffusion model is established for sand-layer penetration grouting. First, the permeability of porous media and average penetration velocity of Bingham slurry were deduced by considering tortuosity. Second, based on the penetration continuity equation, the active steady-state penetration differential equation of Bingham slurry and the pressure distribution function of slurry in the diffusion region were obtained. Finally, combined with the indoor penetration grouting test results, the attenuation law of slurry pressure and the influencing factors of diffusion radius were discussed. The results show that the cylindrical diffusion model of tortuous tubes can better characterize the diffusion process of penetration grouting in the sand layer. The stop condition for diffusion during penetration grouting is the reduction of the pressure gradient of the slurry to its starting value. The slurry pressure attenuation has obvious stages. The slurry pressure attenuation is faster in the area close to the grouting tube. At 50% of the maximum diffusion radius, the pressure attenuation is 70.01~75.41% of the total pressure attenuation within the diffusion region. Increasing the grouting pressure and permeability coefficient and reducing the slurry viscosity ratio can greatly increase the slurry diffusion radius. These results provide a theoretical basis for determining sand grouting parameters in the future.

Penetration Grouting Mechanism of Time-Dependent Power-Law Fluid for Reinforcing Loose Gravel Soil

The time-dependent behavior of power-law fluid has a significant influence on the grouting effects of reinforcing loose gravel soil. In this paper, based on basic rheological equations and the time-dependent behavior of rheological parameters (consistency coefficient and rheological index), rheological equations and penetration equations of time-dependent power-law fluid are proposed. Its penetration grouting diffusion mechanism for reinforcing loose gravel soil was then theoretically induced. A set of indoor experimental devices for simulating penetration grouting was designed to simulate the penetration grouting of power-law fluid with different time-dependent behaviors for reinforcing loose gravel soil. Then, relying on the COMSOL Multiphysics platform and Darcy’s law, three-dimensional numerical calculation programs for this mechanism were obtained using secondary-development programming technology. Thus, the numerical simulations of the penetration grouting process of power-law fluid with different time-dependent behaviors for reinforcing loose gravel soil were carried out. This theoretical mechanism was validated by comparing results from theoretical analyses, indoor experiments, and numerical simulations. Research results show that the three-dimensional numerical calculation programs can successfully simulate the penetration diffusion patterns of a time-dependent power-law fluid in loose gravel soil. The theoretical calculation values and numerical simulation values of the diffusion radius obtained from this mechanism are closer to indoor experimental values than those obtained from the penetration grouting diffusion theory of power-law fluid without considering time-dependent behavior. This mechanism can better reflect the penetration grouting diffusion laws of a power-law fluid in loose gravel soil than the theory, which can provide theoretical support and guidance for practical grouting construction.

Influence of Coupling Effects of Time and Water‐to‐Cement Ratio on Rheological Properties of Bingham Cement Grouts

Time and water‐to‐cement ratio have significant influences on rheology of cement grouts. In order to study effects of time and water‐to‐cement ratio on rheology of Bingham cement grouts, taking Bingham cement grouts widely used in practical engineering (cement grouts with water‐to‐cement ratio of 0.75–1.25) as research object, some rheological experiments of five cement grouts with water‐to‐cement ratio of 0.8, 0.9, 1.0, 1.1, and 1.25 were carried out at six moments of 0, 5, 10, 20, 30, and 60 minutes, respectively. Combining theoretical discussion with numerical analysis, influence of coupling effects of time and water‐to‐cement ratio on rheological properties of Bingham cement grouts was discussed. Results show that at the level of α = 0.05, time has a significant influence on plastic viscosity but has no significant influence on the yield stress of Bingham cement grouts. Water‐to‐cement ratio has a significant influence on both plastic viscosity and yield stress. Exponential models obtained by comprehensive analysis from statistical theory, practical applicability, and accuracy are the optimal models to describe quantitative change in the relationship of coupling effects of time and water‐to‐cement ratio on plastic viscosity and yield stress of Bingham cement grouts. The rheological equation considering coupling effects of time and water‐to‐cement ratio of Bingham cement grouts is constructed. Research achievements not only have certain theoretical significance to the development and improvement of fluid mechanics and theoretical system of penetration grouting but also provide theoretical support and technical reference for practical grouting engineering and also have certain practical significance for solving or improving the practical engineering problems.

Study on Penetration Grouting Mechanism Based on Newton Fluid of Time-Dependent Behavior of Rheological Parameters

Grouting mechanism is one of the important factors on the grouting effects of practical projects. At present, the vast majority of Newton fluid penetration grouting mechanisms are considering that the viscosity of Newton fluid during the grouting whole process was constant, so the theoretical diffusion radius calculated by them is far greater than the actual measurements in the grouting engineering. Carrying out theoretical analysis and experimental research, the rheological equation and seepage motion equation for Newton fluid of time-dependent behavior of rheological parameters were established; then, the penetration grouting mechanism of them was deduced. What is more, they were validated by means of designing the grouting verifying experiments. Experiment results show that the theoretical diffusion radius calculated by the formula of diffusion radius of penetration grouting mechanism based on Newton fluid of time-dependent behavior of rheological parameters was in accordance with the change regulation of the actual measurement diffusion radius by grouting experiments. Their difference within the range of 15% is far less than about 80% change between the theoretical diffusion radius calculated by the Maag formula and the actual measurement radius. In general, it can reflect the grout infiltration laws that Newton fluid changes with time. Therefore, research achievements may not only be able to provide a strong theoretical basis for perfecting the penetration grouting mechanism but also play a reference guiding role for the theoretical research, design, and construction in the grouting technique.

Experimental analysis of penetration grouting in umbrella arch method for tunnel reinforcement

The umbrella arch method (UAM) is conventionally applied to reinforce the tunnel face when difficult geologic conditions such as water inflow and shallow overburden are encountered. Cement-based grouting is normally used with the UAM to ensure waterproofing or local reinforcement of the tunnel structure. In the present study, the corresponding rheological flow of the penetration grouting in the jointed rock masses was analyzed by modeling field conditions as closely as possible. For this, a special experimental apparatus simulating pipe and grout injection holes in jointed rock masses was developed to investigate the penetration and spreading phenomenon of grout. Grout filling and spreading within the rock joint was recorded and compared with the available analytical solutions according to various parameters such as aperture width and pressure difference. Finally, future work that will entail additional tests of joint roughness and persistence is also discussed.

Experimental Study on Vacuum Grouting in Silty Sand Stratum

Vacuum grouting is a new grouting method to control the groundwater in geotechnical engineering, which is often used in the strata where penetration grouting is difficult to reach an expected slurry diffusion radius, such as sand and silt strata. There are some theoretical studies about the influence of the vacuum field on the law of the slurry diffusion. However, the research on soil properties is rare. In this paper, through a self-designed grouting device, grouting in the silty sand after vacuum field action is studied. The test results indicate that with the increase in vacuum degree, the grouting capacity has an obvious improvement. When the vacuum degree is −15 kPa, the grouting capacity increased by 45.9% compared with the blank control group (0 kPa). Then, through the thermogravimetric analyzer and zeta potential meter the change of bound water and electric double layer in the silty sand after the effect of the vacuum field through a small device is studied. The results show that the effect of the vacuum field could make an influence on free water and loosely bound water, but the change of firmly bound water is unnoticeable. With the change of the vacuum degree, the variation of the water is increased. When the vacuum degree is −15 kPa, compared with the blank control group, the variable weight of free water is 5.79% and loosely bound water is 2.86%. As the bound water has a relationship with the effective void ratio, it can be inferred that the vacuum field may have an effect on the permeability coefficient of silty sand. These conclusions provide a reference for the theoretical study of vacuum grouting.

An Experimental Study on the Reinforcement of Silt with Permeable Polyurethane by Penetration Grouting

To meet the demand of antiseepage and reinforcement of soil dams, a kind of permeable polyurethane grouting material was developed. A visual steady‐pressure grouting test device was designed to study the law of polyurethane diffusion and reinforcement in silt under different pressure, and the interaction mechanism of grout and soil body structure was explored microscopically. The results showed that, with the increase in the grouting pressure, the diffusion speed rose, and the diffusion pattern of grout in the soil also changed from permeation diffusion to permeation splitting. Under the effect of grouting pressure, more tiny cracks will occur in the soil structure, leading to the use of more grout, thus increasing the strength of the consolidated soil by more than 10 times. The results of SEM‐EDS and mercury intrusion test proved that the polyurethane had a significant filling effect on the soil structure, which could effectively reduce the porosity of the soil and cement the soil particles through wrapping, complexing, and hydrogen bonding, thereby improving the soil properties. Moreover, the results revealed from a microscopic perspective that the grouting altered the pore structure of the soil structure through the seepage‐erosion‐splitting coupling effect, but when the grouting pressure exceeded 0.4 MPa, the soil particle and grout would be partially remixed and arranged closely, showing a phenomenon of jet grouting. Finally, the material was used in engineering practice, achieving a satisfactory grouting treatment effect.

Modified Maag’s Spherical Diffusion Model of Vacuum Penetration Grouting

The penetration grouting is very widely used in geotechnical engineering nowadays, but the slurry diffusion radius is not long enough because of low grouting pressure. The vacuum grouting method is proposed to solve this problem. However, there is no diffusion theory model of vacuum grouting, which makes the practical application lack scientific basis. In this paper, the distribution law of vacuum negative pressure in soil is deduced. Then, the boundary conditions of Maag’s spherical diffusion model are modified by the vacuum pressure distribution law. After that, the vacuum modification model is deduced. Finally, Maag’s model and modified model are analyzed according to a published experiment, which proves that the vacuum modification model is suitable for predicting the slurry diffusion of vacuum grouting. The proposed model provides a reference for the theoretical study of vacuum grouting.

Grouting reinforcement mechanism and experimental study of cement quick-setting slurry infiltration

According to the sand treatment of cement single liquid penetrant reinforcing effect is poor and the problem of quick setting slurry splitting grouting to control the deformation of the ground surface. For the study on the C-S grouting reinforcement master the quantitative relationship between the factors and the physical and mechanical properties of reinforcement. Choose the cement water glass fast setting slurry. By using different injection medium effective diameter and different grouting pressure conditions, carry out sand grouting test. Study on the variation law of single axial compressive strength and permeability coefficient of stone body strengthened by grouting. Through the analysis of the influence of the plasmid size, the grouting pressure and the diffusion distance. It reveals the strengthening factors of C-S grout penetration grouting and the strengthening mechanism of different physical and mechanical indexes, and the quantitative relationship between them is obtained by regression analysis, and using PFC numerical calculation, the article explores the mechanism of grouting reinforcement. The effective diffusion range of cement based quick setting slurry grouting is put forward. The method for determining the parameters of grouting reinforcement is given, and the results are successfully applied in Qingdao Metro. The research results have certain reference significance for the development and improvement of the mechanism of penetration grouting reinforcement.

Development of a Rock Groutability Index Based on the Rock Engineering Systems (RES): A Case Study

Penetration grouting is used to improve rock conditions under dams and foundations. So far no comprehensive ranking has been presented for the rock groutability assessment. However, a need for an index is tangible to classify the jointed rock masses from cement-based grouting conditions point of view. In this paper an attempt has been made to propose a rock groutability index (RGI) based on the rock engineering systems (RES). RES is an approach to evaluate the interrelationship between the factors affecting rock engineering activities. After discussing the rock grouting mechanism and identifying all the effective factors, an interaction matrix is introduced to study the groutability of rock masses. Thereafter, the interaction intensity and dominance of each factor in the system is determined to classify these factors. As a result, an index is presented to predict the groutability potential of rock masses. Bakhtiari Dam of Iran was selected as a case study and the proposed index was used to rank the seven geological units of Sarvak formation in this dam. It was observed that the rock groutability index could suitably predict rock masses condition from grouting point of view. For the purpose of evaluation, cross correlations was carried out between the Lugeon values with RGI. It was showed that with increasing Lugeon values the RGI decreases linearly with good correlation coefficients.

Research on Grouting Experiment in Aeolian Sand Tunnel

Portland cement, superfine cement and modified sodium silicate have been taken as grouting materials in the aeolian sand tunnel which is characterized by single particle, bad gradation and loose structure. In this paper, penetration grouting and rotary jet grouting have been adopted in site grouting experiment, whose effects are tested by excavation sampling test and field excavation detection. The grouting feature of aeolian sand formation has been revealed. In the meantime, the applicability of different kinds of grouting materials in aeolian sand tunnel have been clarified which provides useful significance and reference value on the selection of grouting parameter and construction in aeolian sand tunnel.

Penetration grouting reinforcement of sandy gravel

To study the relationship between grouting effect and grouting factors, three factors (seven parameters) directionless pressure and small cycle grouting model experiment on sandy gravel was done, which was designed according to uniform design method. And regressing was applied to analysis of the test data. The two models test results indicate that when the diffusing radius of grout changes from 26 to 51 cm, the grouted sandy gravel compressing strength changes from 2.13 to 12.30 MPa; the relationship between diffusing radius(R) and water cement ratio(m), permeability coefficient(k), grouting pressure(p), grouting time(t) is R=19.953m0.121k0.429p0.412t0.437; the relationship between compressing strength(P) and porosity(n), water cement ratio, grouting pressure, grouting time is P=0.984n0.517m−1.488p0.118t0.031. So the porosity of sandy gravel, the permeability coefficient of sandy gravel, grouting pressure, grouting time, water cement ratio are main factors to influence the grouting effect. The grouting pressure is the main factor to influence grouting diffusing radius, and the water cement ratio is the main factor to influence grouted sandy gravel compressing strength.